When you try to add a ESXi host on a EVC enabled cluster it could happen that you might encounter with below error:

The host cannot be admitted to the cluster's current Enhanced vMotion Compatibility mode. Powered-on or suspended virtual machines on the host may be using CPU features hidden by that mode.

The error is self-explanatory that there are few VM’s which are powered on and are using some features which the underlined EVC which is enabled on the cluster doesn’t support.

So, to resolve this issue we end up with powering off all the VM’s on that host to add the host successfully to the EVC enabled cluster.

Have you ever thought what happens on the ESXi host when EVC is enabled on the Cluster?

How the VM’s will come to know what features of CPU with this EVC mode are available on the ESXi host?

Alright here is the answer for those questions.

When we enable EVC mode on the ESXi host /etc/vmware/config is the file which will get updated with all the CPUID’s /features that the selected EVC mode will support.

So how does these files look like?

Without EVC enable:

With EVC enabled:

To fix the above issue you can copy this file from the ESXi host which is already a part of EVC enabled cluster to the ESXi host which you want to add into the same cluster.

I hope this blog will be useful for your daily work.

Happy learning 🙂

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